<template>
    <div class="pagination">
        <button :disabled="pageNum == 1" @click="$emit('handlePageNo',pageNum - 1)">上一页</button>
        <button v-if="startNumAndEndNum.start > 1" @click="$emit('handlePageNo',1)" :class="{active: pageNum == 1}">1</button>
        <button v-if="startNumAndEndNum.start > 2">···</button>

        <button v-for="(page,index) in startNumAndEndNum.end" :key="index" 
                v-if="page >= startNumAndEndNum.start"
                @click="$emit('handlePageNo',page)"
                :class="{active: pageNum == page}">
                    {{page}}
        </button>

        <button v-if="startNumAndEndNum.end < totalPage-1">···</button>
        <button v-if="startNumAndEndNum.end < totalPage " @click="$emit('   ',totalPage)" :class="{active: pageNum == totalPage}">{{totalPage}}</button>
        <button :disabled="pageNum == totalPage" @click="$emit('handlePageNo',pageNum + 1)">下一页</button>

        <button style="margin-left: 30px">共 {{total}} 条</button>
    </div>
</template>

<script>
export default {
    name: "Pagination",
    props: ['pageNum','pageSize','total','continues'],
    computed: {
        totalPage() {
            return Math.ceil(this.total / this.pageSize);
        },
        startNumAndEndNum() {
            const {continues,pageNum,total} = this;
            let start, end = 0;
            if(continues > this.totalPage) {
                start = 1;
                end = this.totalPage;
            }else {
                start = pageNum - parseInt(continues / 2);
                end = pageNum + parseInt(continues / 2);

                if(start < 1) {
                    start = 1;
                    end = continues;
                }

                if(end > this.totalPage) {
                    end = this.totalPage;
                    start = this.totalPage - continues + 1;
                }
            }
            return {start,end};
        }
    }
}
</script>

<style lang="less" scoped>
.pagination {
    text-align: center;
    button {
        margin: 0 5px;
        background-color: #f4f4f5;
        color: #606266;
        outline: none;
        border-radius: 2px;
        padding: 0 4px;
        vertical-align: top;
        display: inline-block;
        font-size: 13px;
        min-width: 35.5px;
        height: 28px;
        line-height: 28px;
        cursor: pointer;
        box-sizing: border-box;
        text-align: center;
        border: 0;

        &[disabled] {
            color: #c0c4cc;
            cursor: not-allowed;
        }

        &.active {
            cursor: not-allowed;
            background-color: #409eff;
            color: #fff;
        }
    }
}
.active {
    background: skyblue;
}
</style>
